/Engine/Plugins/Experimental/PlatformCrypto/Source/PlatformCryptoTypes/Public/PlatformCryptoTypes.h
For ciphers that support authentication tags, you may call this function to retreive the AuthTag after Finalize is called successfully. This will fail for ciphers that do not support AuthTags.
[EPlatformCryptoResult](API\Plugins\PlatformCryptoTypes\EPlatformCryptoResult) GenerateAuthTag ( const [TArrayView](API\Runtime\Core\Containers\TArrayView)< uint8 > OutAuthTag, int32 & OutAuthTagBytesWritten ) const